Download Unit_Phys_2_nuclear_fusion__fission

Unit Physics 2
Candidates should use their skills, knowledge and
understanding of how science works:
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GCSE
Text
Book
Revision
Guide
Nuclear fission
a) There are two fissionable substances in common
use in nuclear reactors: uranium-235 and plutonium239.
b) Nuclear fission is the splitting of an atomic nucleus.
c) For fission to occur, the uranium-235 or plutonium239 nucleus must first absorb a neutron.
Additional guidance:
Candidates should be able to explain why the early
Universe contained only hydrogen but now contains a large
variety of different elements.
The term ‘radiation pressure’ will not be required.
Candidates should be familiar with the chart on the next page
that shows the life cycles of stars.
Additional guidance:
Candidates should be able to sketch or complete a labelled
diagram to illustrate how a chain reaction may occur.
d) The nucleus undergoing fission splits into two
smaller nuclei and two or three neutrons and energy is
released.
e) The neutrons may go on to start a chain reaction.
Nuclear fusion
a) Nuclear fusion is the joining of two atomic nuclei to
form a larger one.
b) Nuclear fusion is the process by which energy is
released in stars.
c) Stars form when enough dust and gas from space is
pulled together by gravitational attraction. Smaller
masses may also form and be attracted by a larger
mass to become planets.
d) During the ‘main sequence’ period of its life cycle a
star is stable because the forces within it are balanced.
e) A star goes through a life cycle. This life cycle is
determined by the size of the star.
f) Fusion processes in stars produce all of the naturally
occurring elements. These elements may be
distributed throughout the Universe by the explosion of
a massive star (supernova) at the end of its life.
Strengths:
Weaknesses:
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